Stamper manufacturing method

ABSTRACT

According to one embodiment, a three dimensional structure of a stamper is subject to etch by supplying a pulsed electric currentelectric current to the surface of the stamper.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2009-141430, filed Jun. 12, 2009; and No. 2010-116927, filed May 21, 2010; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a method of manufacturing a stamper for use in producing a large quantity of data recording media by transferring patterns by means of injection molding, imprinting, or the like.

BACKGROUND

Recently, the recording capacity of data recording apparatuses has been increased by increasing the recording density of a magnetic recording medium. As a magnetic recording medium for achieving a high recording density, a discrete-type magnetic recoding (discrete track recording [DTR]) medium having patterns including a magnetic portion and nonmagnetic portion on a plurality of, e.g., concentrically formed data recording tracks is known.

A method of manufacturing this magnetic recording medium adopts nanoimprinting, injection molding, or the like using a nickel (Ni) stamper as disclosed in, e.g., Patent Reference 1 as a metal mold.

As the recording density of the discrete-type magnetic recording medium increases, the stamper for use in the manufacture of the medium is beginning to require micropatterning that forms three-dimensional patterns at a track pitch of 100 nm or less as disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2008-12705.

When the density increases as the track pitch of the three-dimensional patterns decreases as described above, however, sufficiently wide projecting portions are necessary to maintain the performance of write/read to the medium projecting portions with respect to the narrow pitch. Accordingly, finer recess patterns must be written by an electron beam. Unfortunately, the limitation of an electron-beam lithography apparatus makes it difficult to write grooves of a few nanometers. This makes it impossible to obtain a high-density master in the future.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various feature of the embodiments will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate the embodiments and not to limit the scope of the invention.

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G and 1H are sectional exemplary views for explaining an embodiment of a stamper manufacturing method;

FIGS. 2A, 2B, 2C and 2D are sectional exemplary views for explaining the embodiment of the stamper manufacturing method;

FIG. 3 is an exemplary view of an electroforming apparatus usable in the embodiment;

FIGS. 4A, 4B, 4C, 4D, 4E and 4F are sectional exemplary views showing embodiments of method for manufacturing a magnetic recording medium; and

FIG. 5 is a view showing an embodiment of a magnetic recording/reproduction apparatus capable of incorporating the magnetic recording medium.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to the accompanying drawings.

In general, according to one embodiment, a stamper processing method according to the embodiment etches a three-dimensional structure of a stamper by supplying a pulsed electric current to the surface of the stamper.

According to one embodiment, a stamper manufacturing method forms first, second, and third stampers by transferring three-dimensional patterns of a master.

In forming the third stamper, the stamper processing method described above can be used to process the three-dimensional patterns.

First, a first conductive layer is formed on the surface of a master having three-dimensional patterns, a first electroformed layer is formed on the first conductive layer, and the first electroformed layer and first conductive layer are separated from the master, thereby forming a first stamper onto which the three-dimensional structure of the master is transferred.

Subsequently, a first release layer is formed on the surface of the first stamper, a second conductive layer is formed on the first release layer, a second electroformed layer is formed on the second conductive layer, and the second electroformed layer and second conductive layer are separated from the first stamper, thereby forming a second stamper onto which the three-dimensional structure of the first stamper is transferred.

Furthermore, a second release layer is formed on the second stamper, a third conductive layer is formed on the second release layer, a third electroformed layer is formed on the third conductive layer, and the third electroformed layer and third conductive layer are separated from the second stamper, thereby forming a third stamper onto which the three-dimensional structure of the second stamper is transferred.

The stamper manufacturing method according to the embodiment is characterized by etching the three-dimensional structure of the third stamper by supplying a pulsed electric current to the surface of the third stamper.

In the one embodiment, plating metal deposition caused by a positive pulsed electric current and plating metal etching caused by a reverse pulsed electric current occur repetitively. When a pulsed electric current is supplied to the three-dimensional structure of nano-patterns, plating metal etching occurs with priority on plating metal deposition. Consequently, smooth etching can be performed.

When using the embodiment, the third stamper is etched by supplying a pulsed electric current. Since three-dimensional nano-patterns can be etched, projecting portions of the three-dimensional structure can be made narrower so that the line edge roughness is decreased. This prevents the formation of a rough three-dimensional surface, and the formation of, e.g., rough spiral or concentric three-dimensional patterns. Also, dust particles are removed by the repetition of plating metal deposition and etching. In addition, the stamper and transferred patterns are roughened and damaged less. Since this increases the durability of the stamper, the number of duplication cycles is greatly increased.

Furthermore, the three-dimensional structure can have periodic patterns having a track pitch of 100 nm or less, e.g., 75 to 90 nm.

The etching is performed in a plating solution.

Ni sulfamate can be used as the plating solution. It is also possible to use, e.g., an Ni sulfate-Ni chloride solution mixture (Watts bath).

A pulsed electric current can be supplied at a frequency of 100 Hz or more, e.g., 500 to 5,000 Hz and an accumulated current of 0.1 to 5.0 μA·min/mm² by alternately supplying a positive electric current and reverse electric current.

One embodiment will be explained in more detail below with reference to the accompanying drawing.

FIRST EMBODIMENT

FIGS. 1A to 1H are sectional exemplary views for explaining a stamper manufacturing method according to the first embodiment. Stampers are manufactured by the following process by using, e.g., a coating apparatus, lithography apparatus, developing apparatus, deposition apparatus, and electroforming apparatus.

First, as shown in FIG. 1A, the coating apparatus is used to coat a master substrate 11 such as a glass or Si base with a resist by, e.g., spin coating, thereby forming a resist layer 12.

Then, as shown in FIG. 1B, the lithography apparatus is used to form a latent image by irradiating the resist layer formed by the coating apparatus with an electron beam (EB), and the developing apparatus is used to develop the resist layer 12 having undergone the latent image formation performed by the lithography apparatus, thereby forming three-dimensional patterns. The substrate formed through the series of steps described above will be called a master 10.

Subsequently, as shown in FIG. 1C, the deposition apparatus is used to form a conductive film 13 on the three-dimensional patterns of the master 10. In addition, as shown in FIG. 1D, the electroforming apparatus is used to form an electroformed layer 14 on the conductive film 13 by electroplating performed in an Ni sulfamate bath. Conductive film 13 and electroformed layer 14 is separated from the master 10, thereby manufacturing a father stamper 15 consisting of conductive film 13 and electroformed layer 14 as a first stamper shown in FIG. 1E.

Then, as shown in FIG. 1F, an oxide film 16 is formed as a release layer on the three-dimensional patterns of the father stamper 15 by, e.g., anodic oxidation or oxygen plasma ashing. And then an electroformed layer 17 made of Ni is formed after a conductive film (not shown) is formed on the oxide film 16 as shown in FIG. 1G, and separated the electroformed layer 17 and the conductive film (not shown) from the first stamper to duplicate a mother stamper 18 as a second stamper shown in FIG. 1H.

Subsequently, as shown in FIG. 2A, an oxide film 19 is formed as a release layer on the three-dimensional patterns of the mother stamper 18 by, e.g., anodic oxidation or oxygen plasma ashing. After that, an electroformed layer 20 made of Ni is formed after a conductive film (not shown) is formed on the oxide film 19 as shown in FIG. 2B, and separated the electroformed layer 20 and the conductive film (not shown) from the second stamper to duplicate a son stamper 21 as a third stamper as shown in FIG. 2C.

The surface of the son stamper 21 thus obtained is dipped in an Ni sulfamate bath, and a pulsed electric current is supplied under the following conditions, thereby etching the three-dimensional surface patterns. The electroforming apparatus is used in this etching.

The three-dimensional pattern structure of the son stamper used had a pitch of 85 nm, a height of 50 nm, and a width of 30 nm.

Frequency: 500 Hz

On-Time: 1 ms

Off-Time: 1 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 1.0 μA·min/mm2

The three-dimensional pattern structure of a pulse etching son stamper 22 obtained as described above had a height of 50 nm and a width of 18 nm as shown in FIG. 2D, i.e. the three-dimensional pattern structure was etched by 12 nm compared with that before the pulsed electric current was supplied. Furthermore, the line edge roughness (LER) after the etching had decreased by 0.35 nm compared with that before the etching.

After that, a protective film was formed on the three-dimensional pattern surface by spin coating and dried. A stamper for mass-transfer of media as a final form is completed through steps such as lower-surface polishing and punching as needed.

As the thin conductive film 13 described above, it is possible to use a material mainly containing Ni because the material has high physical strength, high mechanical strength, high resistances against corrosion and wear, and high adhesion to Ni as the electroforming material. Also, Ni or a material containing Ni and one of Co, S, B, and P can be used as the electroformed layer 14, 17, and 20.

FIG. 3 is a schematic view showing the arrangement of an example of the electroforming apparatus for use in the embodiment.

For example, when forming an electroformed layer on a master, father stamper, or mother stamper (referred to as a matrix 150 hereinafter) having three-dimensional patterns as shown in FIG. 3 by dipping the matrix 150 in a sulfamic acid solution, a jig 152 holds the outer periphery of the matrix 150. The jig 152 is supported by a rotating shaft 54, and the rotating shaft 54 can be rotated by a motor 56. That is, the motor 56 rotates the matrix 150 held by the jig 152. The matrix 150 held by the jig 152 is dipped in a plating solution 64 contained in a vessel 62 of an electroforming apparatus 60. A case 65 in which Ni pellets 66 are deposited is dipped in the plating solution 64 in an electroforming bath 62 of the electroforming apparatus 60. In the vessel 62, a partition 67 having an opening isolates the case 65 from the side on which the matrix 150 is dipped in the plating solution 64. Note that the matrix 150 to be plated is positioned so as to face the opening of the partition 67. A rectifier 70 applies a positive potential to the case 65 and a negative potential to the matrix 150, and a discharge nozzle 68 discharges a plating solution supplied through a filter from a control bath (not shown) to a portion between the opening and matrix 150, thereby forming an electroformed layer on the matrix 150. The plating solution discharged from the discharge nozzle 68 fills the room on the side of the matrix 150, which is partitioned by the partition 67, and then overflows to fill the room on the side of the case 65. After that, the plating solution is returned to the control bath (not shown) from a drain 69 so as to balance the drain amount with the discharge amount. The plating solution is thus circulated.

When using this electroforming apparatus in the etching using a pulsed electric current according to the embodiment, a DC power supply capable of generating a pulse waveform can be used instead of the rectifier.

SECOND EMBODIMENT

After a son stamper 21 was manufactured following the same procedures as in First Embodiment, the surface of the son stamper was dipped in the above-mentioned Ni sulfamate bath, and a pulsed electric current was supplied under the following conditions, thereby etching the three-dimensional surface patterns.

The three-dimensional pattern structure of the son stamper used had a pitch of 85 nm, a height of 50 nm, and a width of 30 nm.

Frequency: 500 Hz

On-Time: 1 ms

Off-Time: 1 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 0.2 μA·min/mm²

The three-dimensional pattern structure of a pulse etching son stamper obtained as described above had a height of 50 nm and a width of 25 nm, i.e., the three-dimensional pattern structure was etched by 5 nm compared with that before the pulsed electric current was supplied. The LER after the etching had decreased by 0.91 nm compared with that before the etching.

THIRD EMBODIMENT

After a son stamper 21 was manufactured following the same procedures as in First Embodiment, the steps shown in FIGS. 1E to 1H and 2A to 2C were repeated by using this son stamper as a master, thereby manufacturing a grandson stamper. The surface of the grandson stamper thus obtained was dipped in the above-mentioned Ni sulfamate bath, and a pulsed electric current was supplied under the following conditions, thereby etching the three-dimensional surface patterns.

The three-dimensional pattern structure of the grandson stamper used had a pitch of 85 nm, a height of 47 nm, and a width of 27 nm.

Frequency: 500 Hz

On-Time: 1 ms

Off-Time: 1 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 1.6 μA·min/mm²

The three-dimensional pattern structure of a pulse etching grandson stamper obtained as described above had a height of 40 nm and a width of 8 nm, i.e., the three-dimensional pattern structure was etched by 19 nm compared with that before the pulsed electric current was supplied. The LER after the etching had decreased by 1.30 nm compared with that before the etching.

FOURTH EMBODIMENT

After a son stamper 21 was manufactured following the same procedures as in First Embodiment, the steps shown in FIGS. 1E to 1H and 2A to 2C were repeated by using this son stamper as a master, thereby manufacturing a grandson stamper. The surface of the grandson stamper thus obtained was dipped in the above-mentioned Ni sulfamate bath, and a pulsed electric current was supplied under the following conditions, thereby etching the three-dimensional surface patterns.

The three-dimensional pattern structure of the grandson stamper used had a pitch of 85 nm, a height of 47 nm, and a width of 27 nm.

Frequency: 5,000 Hz

On-Time: 0.1 ms

Off-Time: 0.1 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 4.8 ∥A·min/mm²

The three-dimensional pattern structure of a pulse etching grandson stamper obtained as described above had a height of 35 nm and a width of 10 nm, i.e., the three-dimensional pattern structure was etched by 17 nm compared with that before the pulsed electric current was supplied. The LER after the etching had decreased by 0.03 nm compared with that before the etching.

FIFTH EMBODIMENT

After a son stamper 21 was manufactured following the same procedures as in First Embodiment, the steps shown in FIGS. 1E to 1H and 2A to 2C were repeated by using this son stamper as a master, thereby manufacturing a grandson stamper. The surface of the grandson stamper thus obtained was dipped in the above-mentioned Ni sulfamate bath, and a pulsed electric current was supplied under the following conditions, thereby etching the three-dimensional surface patterns.

The three-dimensional pattern structure of the grandson stamper used had a pitch of 85 nm, a height of 47 nm, and a width of 27 nm.

Frequency: 5,000 Hz

On-Time: 0.1 ms

Off-Time: 0.1 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 6.0 ∥A·min/mm²

The three-dimensional pattern structure of a pulse etching grandson stamper obtained as described above had a height of 20 nm and a width of 15 nm, i.e., the three-dimensional pattern structure was etched by 12 nm compared with that before the pulsed electric current was supplied. The LER after the etching increased by 0.56 nm compared with that before the etching.

SIXTH EMBODIMENT

After a son stamper 21 was manufactured following the same procedures as in First Embodiment, the surface of the son stamper was dipped in the above-mentioned Ni sulfamate bath, and a pulsed electric current was supplied under the following conditions, thereby etching the three-dimensional surface patterns.

The three-dimensional pattern structure of the son stamper was formed by a lithography apparatus to a dot shape having a pitch of 90 nm, a height of 37 nm, and a diameter of 50 nm.

Frequency: 500 Hz

On-Time: 1 ms

Off-Time: 1 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 0.2 μA·min/mm²

The three-dimensional pattern structure of a pulse etching son stamper obtained as described above had a height of 35 nm and a diameter of 40 nm, i.e., the three-dimensional pattern structure was etched by 10 nm in diameter compared with that before the pulsed electric current was supplied. The three-dimensional pattern structure of the dot shape having a regular prism form was changed into a cylindrical form and the edge of the dot shape was decreased after the etching compared with that before the etching.

Since the stamper manufactured by this embodiment Exhibited decreased LER and the edge of the dot shape pattern was decreased, the number of duplication cycles is greatly increased. In stamper duplication, the transfer efficiency is generally less than 100%. When repeating duplication, therefore, the patterns of the stamper wear and increase the roughness, and this exerts an adverse effect on a later imprinting process. When using the embodiment, however, the roughness of the manufactured stamper is decreased. This makes it possible to greatly increase the number of duplication cycles; more specifically, the number of duplication cycles is twice that of a conventional stamper.

Also, the number of dust particles adhering to the patterns of the stamper manufactured by this embodiment was counted by an optical reflection microdefect testing apparatus, e.g., Micro Max manufactured by Vision Psytec. As a result, 115 dust particles were found in the conventional duplicating method, whereas 18 dust particles were found in the etching method of this proposal. That is, the embodiment achieves the effect of removing dust particles by etching using a pulsed electric current.

COMPARATIVE EXAMPLE 1

After a son stamper 21 was manufactured following the same procedures as in First Embodiment, the surface of the obtained son stamper 21 was dipped in the above-mentioned Ni sulfamate bath, and a pulsed electric current was supplied under the following conditions, thereby etching the three-dimensional surface patterns.

The three-dimensional pattern structure of the son stamper used had a pitch of 85 nm, a height of 50 nm, and a width of 30 nm.

Frequency: 50 Hz

On-Time: 100 ms

Off-Time: 100 ms

Positive (deposition-side) electric current: 1.00 A

Reverse (dissolution-side) electric current: 0.99 A

Accumulated current: 1.0 μA·min/mm²

The three-dimensional pattern structure of a pulse etching grandson stamper obtained as described above had a height of 10 nm and a width of 10 nm, i.e., the patterns disappeared.

An example of a DTR medium manufacturing method will briefly be explained below with reference to FIGS. 4A to 4F.

DTR media were manufactured by the method shown in FIGS. 4A to 4F by using the stampers according to the first embodiment, second embodiment, and comparative example.

A magnetic layer 51 is deposited on a substrate 50, and coated with a resist 52 (FIG. 4A). As the substrate, it is possible to use, e.g., a glass substrate, an Al-based alloy substrate, ceramic, carbon, an Si single-crystal substrate having an oxidized surface, or a substrate obtained by plating any of these substrates with NiP or the like. Examples of the glass substrate are amorphous glass and crystallized glass. General-purpose soda lime glass or alumino silicate glass can be used as the amorphous glass. Lithium-based crystallized glass can be used as the crystallized glass. As the ceramic substrate, it is possible to use a general-purpose sintered product mainly containing, e.g., aluminum oxide, aluminum nitride, or silicon nitride, or a fiber-reinforced product of this sintered product. As the substrate, it is also possible to use a substrate obtained by forming an NiP layer on the surface of any of the above-mentioned metal substrates and nonmetal substrates by using plating or sputtering. Also, although sputtering alone will be explained below as a method of forming a thin film on the substrate, the same effect can be obtained by, e.g., vacuum deposition or electroplating. A magnetic layer, particularly, a perpendicular magnetic recording layer is made of a material mainly containing Co, containing at least Pt, and further containing an oxide. As this oxide, silicon oxide and titanium oxide are particularly favorable. The perpendicular magnetic recording layer can have a structure in which magnetic grains (crystal grains having magnetism) are dispersed in the layer. The magnetic grain can have a columnar structure vertically extending through the perpendicular magnetic recording layer.

Then, a stamper 30 having three-dimensional patterns is prepared, the pattern surface of the stamper 30 is opposed to the resist 52, and the patterns of the stamper 30 are transferred onto the resist 52 by imprinting (FIG. 4B). In this imprinting, the stamper is urged against the substrate coated with the resist, and the patterns are transferred onto the resist by curing it. The stamper and substrate are set to oppose the three-dimensional surface of the stamper to the resist film side of the substrate. Note that as the resist, it is possible to use, e.g., a UV-curing resin or a general resist material mainly containing, e.g., novolak. When using the UV-curing resin, the stamper material is preferably quartz or a resin that transmits light. The resist can be cured by ultraviolet irradiation. Ultraviolet light can be emitted by using, e.g., a high-pressure mercury lamp. When using the general resist mainly containing, e.g., novolak, a material such as Ni, quartz, Si, or SiC can be used as the stamper material. The resist can be cured by applying heat, pressure, or the like. Subsequently, the resist residue remaining in recesses of the resist 52 is removed by reactive ion etching using gaseous oxygen (FIG. 4C). A plasma source is preferably inductively coupled plasma (ICP) capable of generating a high-density plasma at a low pressure. However, it is also possible to use electron cyclotron resonance (ECR) plasma or a general parallel-plate RIE apparatus. Then, the magnetic layer 51 is etched by ion milling by using patterned resists 52 a as masks (FIG. 4D). The remaining resists 52 a are removed by oxygen asking (FIG. 4E). A DTR medium can be manufactured by filling a nonmagnetic material in the recesses as needed, and forming a protective film 53 on the entire surface (FIG. 4F). The protective layer is formed to prevent corrosion of the perpendicular magnetic recording layer, and damage to the medium surface when a magnetic head comes in contact with the medium. Examples of the material are those containing C, SiO₂, and ZrO₂. The thickness of the protective layer can be 1 to 10 nm.

FIG. 5 is a schematic view showing an example of a magnetic recording/reproduction apparatus that can be manufactured by using the embodiment.

A magnetic recording apparatus (hard disk drive) as shown in FIG. 5 was manufactured by using the obtained DTR medium. This magnetic recording apparatus includes, in a housing 70, a magnetic recording medium (DTR medium) 71 described above, a spindle motor 72 for rotating the magnetic recording medium 71, a head slider 76 incorporating a magnetic head, a head suspension assembly that supports the head slider 76 and includes a suspension 75 and actuator arm 74, and a voice coil motor (VCM) 77 as an actuator of the head suspension assembly.

The spindle motor 72 rotates the magnetic recording medium 71. The head slider 76 incorporates the magnetic head including a write head and read head. The actuator arm 74 is pivotally attached to a pivot 73. The suspension 75 is attached to one end of the actuator arm 74. The head slider 76 is elastically supported via a gimbal formed on the suspension 75. The VCM 77 is formed at the other end of the actuator arm 74. The VCM 77 generates rotating torque around the pivot 73 of the actuator arm 74, thereby positioning the magnetic head in a floated state on an arbitrary radial position of the magnetic recording medium 71.

Note that the embodiment is not limited to the above embodiments, and can variously be modified when practiced without changing the spirit and scope of the invention. Note also that the above-mentioned embodiments have portions in which shapes, numerical values, and the like are different from actual ones, but these factors can appropriately be changed in consideration of known techniques.

Furthermore, the above embodiments include inventions in various stages, so various inventions can be extracted by properly combining a plurality of disclosed constituent elements. For example, even when some of all the constituent elements disclosed in the embodiments are deleted, an arrangement from which these constituent elements are deleted can be extracted as an invention, provided that the problems described in the section of the problems to be solved by the invention can be solved, and the effects described in the section of the effects of the invention can be obtained.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The various modules of the systems described herein can be implemented as software applications, hardware and/or software modules, or components on one or more computers, such as servers. While the various modules are illustrated separately, they may share some or all of the same underlying logic or code. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

1. A stamper manufacturing method comprising: forming a first conductive layer on a surface of a master having a three-dimensional structure; forming a first electroformed layer on the first conductive layer; separating the first electroformed layer and the first conductive layer from the master to form a first stamper onto which the three-dimensional structure of the master is transferred; forming a first release layer on a surface of the first stamper; forming a second conductive layer on the first release layer; forming a second electroformed layer on the second conductive layer; separating the second electroformed layer and the second conductive layer from the first stamper to form a second stamper onto which the three-dimensional structure of the first stamper is transferred; forming a second release layer on a surface of the second stamper; forming a third conductive layer on the second release layer; forming a third electroformed layer on the third conductive layer; separating the third electroformed layer and the third conductive layer from the second stamper to form a third stamper onto which the three-dimensional structure of the second stamper is transferred; and etching the three-dimensional structure of the third stamper by supplying a pulsed electric current to a surface of the third stamper.
 2. The method of claim 1, wherein the three-dimensional structure has a periodical pattern having a track pitch of not more than 100 nm, and the etching is performed in an Ni sulfamate solution, and the pulsed electric current is supplied at a frequency of not less than 100 Hz and an accumulated current of about 0.1 to 5.0 μA·min/mm² by alternately supplying a positive electric current and a reverse electric current.
 3. A stamper processing method of etching a three-dimensional structure of a stamper by supplying a pulsed electric current to a three-dimensional surface of the stamper.
 4. The method of claim 3, wherein the etching is performed in an Ni sulfamate solution, and the pulsed electric current is supplied at a frequency of not less than 100 Hz and an accumulated current of about 0.1 to 5.0 μA·min/mm² by alternately supplying a positive electric current and a reverse electric current. 